Determination of IGF-1 and IGF-2, their degradation products and synthetic analogues in urine by LC-MS/MS

Peptide analysis in doping controls by means of nano-UPLC coupled high resolution/high mass accuracy mass spectrometry provides the state-of-the-art technique in modern sports drug testing. The present study describes a recent application of this technique for the qualitative determination of different urinary insulin-like growth factor (IGF) related peptides. After simultaneous isolation by solid phase extraction and magnetic particle-based immunoaffinity purification, target analytes (IGF-1, IGF-2, Des1-3-IGF-1, R(3)-IGF-1 and longR(3)-IGF-1) were separated by nano-liquid chromatography prior to mass spectrometric detection. Endogenously produced IGF-1 and IGF-2, as well as the degradation product Des1-3-IGF-1, were frequently detected in urine samples from healthy volunteers in a concentration range of 20-400 pg mL(-1). The impact of IGF binding proteins (IGFBPs), being also present in urine, was potentially estimated by an additional ultrafiltration step in the sample preparation procedure. The synthetic analogue longR(3)-IGF-1, which is assumed to be subject to misuse by cheating athletes, was also analysed and detected in fortified urine samples. Besides the intact molecule, an N-terminally truncated degradation product Des1-10-longR(3)-IGF-1 was identified as the more stable target for doping controls using urine samples. The method was validated for qualitative purposes considering the parameters specificity, limit of detection (20-50 pg mL(-1)), recovery (10-35%), precision (<20%), linearity, robustness and stability.     

Sterically Active Electron Pairs in Lead Sulfide? An Investigation of the Electronic and Vibrational Properties of PbS in the Transition Region Between the Rock Salt and the α-GeTe-Type Modifications

Recently, we have investigated the energy landscape of PbS for many different pressures on the ab initio level by using Hartree-Fock and density functional theory to globally search for possible thermodynamically stable and metastable structures. The perhaps most fascinating observation was that besides the experimentally known modification exhibiting the rock salt structure a second minimum exists close-by on the landscape showing the low-temperature α-GeTe-type structure. In the present study, we investigate the possible reasons for the existence of this metastable modification; in particular we address the question, whether the α-GeTe-type modification might be stabilized (and conversely the rock salt modification destabilized) by steric effects of the non-bonding electron pair.     

Bifurcations in a System of Interacting Fronts

We show that the bifurcation scenario in a high-dimensional system with interacting moving fronts can be related to the universal U-sequence which is known from the symbolic analysis of iterated one-dimensional maps. This connection is corroborated for a model of a semiconductor superlattice, which describes the complex dynamics of electron accumulation and depletion fronts. By a suitable Poincaré section we reduce the dynamics to a low-dimensional iterated map, for which in the most elementary case the bifurcation points can be determined analytically.     

Resonant fluorescence emission from the Ge and Cu valence band

Received: 16 March 1996